Seasonal variation in methane and nitrous oxide flux in the Cochin coastal micro tidal estuarine system

3^rd International Conference on Hydrology & Meteorology

September 15-16, 2014 Hyderabad International Convention Centre, India

Akhilesh Vijay, Regina Hershey N, Neelima Vasu and S Bijoy Nandan

Accepted Abstracts: Hydrol Current Res

Abstract :

The Cochin estuary is a micro tidal positive estuary situated on the southwest coast of India, in its banks where the country?s major shipment ports and industrial sectors are located. It is the second largest estuarine system in India, fed by six rivers discharging about 2 x1010 m3y-1 of fresh water. The seasonal distribution of dissolved methane and nitrous oxide in micro tidal Cochin estuarine hydrological system was investigated during the pre-monsoon, monsoon and post-monsoon seasons from August 2013 to July 2014. The surface and bottom samples were investigated extensively from representative estuarine provinces extending from organic loaded riverine discharge to the bar mouth of the Arabian Sea. Dissolved methane in the subsurface water was supersaturated in the entire study area in all the seasons, ranging from a lowest value of 2.9 μmolesl-1 in the post monsoon to highest value of 64.8 μmolesl-1 in the pre monsoon season. The near- bottom waters showed relatively reduced concentrations of methane ranging from 0.3 μmoles/L in the monsoon to 15.5 μmoles/L in pre monsoon. The methane concentration in the Cochin estuarine system is largely determined by in-situ production, inputs from the coastal wetlands and air-water exchange. Low super- saturation of nitrous oxide was observed in the subsurface waters in all the seasons during the study period. The average surface water nitrous oxide concentration ranged from 9.08 nml-1 in the post-monsoon to 20.88 nml-1 in the pre-monsoon. Increased concentrations of dissolved nitrous oxide were observed in the near bottom waters ranging from10.60 nm.l-1 in the postmonsoon to 53.85 nml-1 in the monsoon. Costal estuarine environments of the Cochin seem to be an important source of methane rather than a sink.

Biography :

Akhilesh Vijay is a Senior Research Fellow pursuing his PhD in Dept. of Marine Biology, Microbiology and Biochemistry, CUSAT under the supervision of Dr. S Bijoy Nandan in the topic ?Carbon Sequestration Potential of Coastal Wetlands a Comparative Model?.